Abstract
Several whole genome duplication (WGD) events followed by rediploidization took place in the evolutionary history of vertebrates. Acipenserids represent a convenient model group for investigation of the consequences of WGD as their representatives underwent additional WGD events in different lineages resulting in ploidy level variation between species, and these processes are still ongoing. Earlier, we obtained a set of sterlet (Acipenser ruthenus) chromosome-specific libraries by microdissection and revealed that they painted two or four pairs of whole sterlet chromosomes, as well as additional chromosomal regions, depending on rediploidization status and chromosomal rearrangements after genome duplication. In this study, we employed next generation sequencing to estimate the content of libraries derived from different paralogous chromosomes of sterlet. For this purpose, we aligned the obtained reads to the spotted gar (Lepisosteus oculatus) reference genome to reveal syntenic regions between these two species having diverged 360 Mya. We also showed that the approach is effective for synteny prediction at various evolutionary distances and allows one to clearly distinguish paralogous chromosomes in polyploid genomes. We postulated that after the acipenserid-specific WGD sterlet karyotype underwent multiple interchromosomal rearrangements, but different chromosomes were involved in this process unequally.
Highlights
Whole genome duplications (WGDs), the events resulting in polyploid organisms’ appearance, are not very common among chordate animals [1], but they played a substantial role in early vertebrate evolution [2,3]
We focused on sterlet (Acipenser ruthenus, ARUT), a small sturgeon with 2n = 120, recently characterized by an ongoing rediploidization process after the ancestral acipenserid specific
As sterlet has a high number of chromosomes (2n = 120), which are difficult to distinguish due to weak banding and similar morphologies, we microdissected anonymous chromosomes and identified the position in the karyotype only after subsequent fluorescence in situ hybridization (FISH) experiments (Figures 1 and 2)
Summary
Whole genome duplications (WGDs), the events resulting in polyploid organisms’ appearance, are not very common among chordate animals (in contrast to plants, for instance) [1], but they played a substantial role in early vertebrate evolution [2,3]. WGD in the common ancestor of vertebrates (1R and 2R), which occurred about 500–600 million years ago (Mya) [4,5,6]. Teleosts (bony fishes) underwent their own lineage-specific WGD (TS3R, teleost-specific 3R) about 320 Mya [4]. Polyploidy among extant vertebrate animals quite often occurs in ray-finned fishes and amphibians [3], but it is lacking in mammals and birds (probably because of their sensitivity to gene dosage and other epigenetic effects [1,3]). It was previously shown that fluorescence in situ hybridization (FISH)
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